Validation of a Method for Accurate and Highly Reproducible Quantification of Brain Dopamine Transporter SPECT Studies

In nuclear medicine brain imaging, it is important to delineate regions of interest (ROls) so that the outcome is both accurate and reproducible. The purpose of this study was to validate a new time-saving algorithm (DATquan) for accurate and reproducible quantification of the striatal dopamine transporter (DAT) with appropriate radioligands and SPECT and without the need for structural brain scanning. Methods: In a reconstructed DAT SPECT image, DATquan automatically calculated the ratio at steady state of specifically bound radioligand to nondisplaceable radioligand in tissue (BPND) within striatal ROls that were delineated by use of a semiautomatic template-based alignment approach. DATquan was tested with I-123-N-(3-iodoprop-2E-enyl)-2-beta-carbomethoxy-3 beta-(4-methylphenyl) SPECT images from 15 patients. In each image, ROls were first manually delineated, and then corresponding BPND values were derived by an experienced physician. Afterward, 2 independent novice operators used DATquan to analyze the same 15 images. The resulting DATquan-derived BPND data were compared with the data retrieved by manual delineation to assess the accuracy and reproducibility of DATquan. Also, the operational aspects of DATquan were assessed on the basis of measurements of the mean running time of the algorithm as well as on the basis of quantification of the overlap of the DATquan-delineated ROls obtained by the 2 operators. Results: The mean algorithm running time was 3 min, and the operators' striatal ROls had a mean overlap of more than 82%. DATquan-derived BPND values obtained by the 2 operators showed high agreement (the mean difference was 0.00 [SD, 0.05] in the striatum, 0.02 [SD, 0.26] in the putamen, and 0.03 [SD, 0.43] in the caudate nucleus). The interoperator variability was 2.2% (SD, 1.3%) in the striatum, 11.7% (SD, 9.9%) in the putamen, and 12.9% (SD, 4.0%) in the caudate nucleus. DATquan-derived BPND values showed high agreement with the values manually derived by the experienced delineator. Conclusion: DATquan is a freely available, accurate, and highly reproducible method for quantification of DAT binding in the brain by SPECT. Once implemented in clinics, DATquan will serve as a useful and time-saving tool.